Throttle body sync?

[Whoops]

I was about to buy the Morgan Carbtune Pro 4 and attempt a throttle body sync to see if that smooths out the vibration I felt on my bike when I was able to ride it a couple months ago. I have no idea how to do this job or even if I can do it, but wanted to ask if it is even possible and if that particular tool will work for the CB1100. Searching the forum didn’t get me very far.

Does anyone have any experience doing this on the CB? With this tool? Tips? Tricks? Bueller?

[dave]

Honda recommends that you do not attempt to adjust the sync on the throttle bodies. Unless you can hear misfiring, then the vibration you describe is not caused by your fuel system. If you want to confirm, then remove your spark plugs and inspect them.

[max]

Good question whoops, the throttle body sync is only applicable to an engine when it runs stationary and warmed up.

The adjustment is done on the bypass air passages as opposed to the butterfly valves to make the engine run evenly on all cylinders, the cb1100 probably has these adjustment screws but like Dave mentions not worth touching unless you are familiar with all the synchronizing aspects and how the e.c.u.reacts to them.

As soon as the throttle is opened the butterfly valves negate all stationary adjustments made at the factory and if there are any vibrations are unlikely related to differences in the cylinder contribution unless injectors are not equal which is not a common situation, remembering that our camshafts are supposed to be giving the engine a certain character, which is something i know very little about.

Tracing vibrations could start on the center stand in neutral and slowly building the rev's to note where most vibrations are felt, if any cylinders are not contributing it may be that the vibrations are constant over a wide range of rpm's, other checks could be measuring the cylinder contribution at the exhaust somehow with an audio pickup and a digital oscilloscope with a memory function.

[Lord Popgun]

It is funny that Honda doesn’t want us messing with any adjustments, yet on the ST1300 people do a throttle body sync all the time with great results. I have a a digital tool to do mine although an old school mercury carb stick would do it too.

Personally, I don’t see why it couldn’t be done on the CB. The factory does it.

[max]

Correct Lord Popgun, it certainly can be done as long as you know what to look out for and don't get carried away.
You need the right set of vacuum hoses on top of the throttle bodies ( don't disconnect the sensors by mistake but use the hoses that produce the vacuum used on the bike's system ) and the adjustment is in the bottom of the throttle bodies ( the black screws ) i have done it on my cb919 ( which ran on 3 cylinders stationary when i got it ) very successfully but it makes a difference if you have experience, confidence and the tools ( like know your gauges are in fact indicating the same amount when connected together ) to do the job.

One of the differences with older carbs is that 4 carbs have only 3 adjustment points, so there is a reference built in that cannot be shifted for ever, these throttle bodies have all four so there is a chance that you can keep shifting the balance point in one direction or another, so it would be good to count each adjustment screw's position to the mechanical stop and write down the amount so as to have a baseline to work with as the iacv could be correcting the rpm level trying to maintain 1050 rpm's whilst the adjustments are made and get out of range in an extreme case, so some skills are handy, techs with experience just glance over honda's advice and proceed anyway.

Have tested the sync on mine and have made some very small Unnecessary adjustments, so it can be done but in a deliberate way which i would not advice somebody with not enough experience to undertake so you are absolutely correct as usual.

[PowerDubs_imp]

It is funny that Honda doesn’t want us messing with any adjustments, yet on the ST1300 people do a throttle body sync all the time with great results. I have a a digital tool to do mine although an old school mercury carb stick would do it too.

Personally, I don’t see why it couldn’t be done on the CB. The factory does it.

The factory does it presumably with very expensive calibrated equipment- I would guess on a bench, not each complete engine while running.

The reason they say not to adjust may be some variable due to our purposely mistimed cams.

I would tell the average normal person to leave it alone.

Whatever they are feeling most likely isn't due to TB 'sync'.

The blades angle could be 100% the same- but each cyl filling certainly isn't- by design.

Heck before you want to get into TB adjustments- add fuel first- that smooths things out nicely.

[Charlie Bravo_imp]

I wouldn't think a late-model CB would require a TB synch. I had one done on my '03 Suzi DL1000 with 50k on the clock, but I had bought it pretty cheap and had it in the shop for a cooling system flush and fill, air filter replacement and new plugs.